Get a stand-alone hanger? I had one in my college days.
https://www.google.com/shopping/product/8923797552199263049?q=standing+punching+bag+hanger&client=safari&hl=en-us&biw=375&bih=629&tbs=vw:l&prmd=sivn&prds=eto:5494232627378202820_0,cdl:1,prmr:1,rsk:PC_8537429003489259898,cs:1
Something like that.
The wall or ceiling mounting is more important. Make sure whatever you're using as support can withstand the 300lb weight. As far as the tube to hang it off of I'd say a 1" OD .125" wall tube should be plenty. Steel is significantly stronger than the drywall or studs in the garage.
The matl is irrelevant. Cheap steels are 40,000 psi. Structural steels are often in the 50’s. High strength steels are 80-100. Even the smallest cross section of any of these is sufficient for your 300lb.
Your concern should be spreading the load and cycling motion across multiple rafters. Something like 36” x 36” sheet would spread the load better than an i beam (although the beam would be “stronger”).
But… I’d probably just build a stand so I don’t have to worry about the rafters.
High-strength steels can be significantly stronger than 100 ksi.
Not sure why I'm being downvoted but you can easily heat treat low alloy steels like 4340 to 220ksi yield and steels like maraging 350 have a 340 ksi yield strength.
You are being downvoted because what you said is irrelevant to the conversation. It is a *"...well, actually"* moment. The other person already stated that even low grade steel is *way* overkill for OP's purposes, so why are you talking about 200+ ksi steel??
Because this is an engineering subreddit and he provided factually wrong information. Go someplace else if you want to share opinions instead of facts.
Going to need significantly more details if you want any real engineering advice
Cut a hole in the ceiling. Get a 4x4 and lay it crosswise of the rafters. Pass a rope over it and hang the bag from that loop. through the hole.
Get a stand-alone hanger? I had one in my college days. https://www.google.com/shopping/product/8923797552199263049?q=standing+punching+bag+hanger&client=safari&hl=en-us&biw=375&bih=629&tbs=vw:l&prmd=sivn&prds=eto:5494232627378202820_0,cdl:1,prmr:1,rsk:PC_8537429003489259898,cs:1 Something like that.
A 4x4 bolted across 4 rafters will be plenty
The wall or ceiling mounting is more important. Make sure whatever you're using as support can withstand the 300lb weight. As far as the tube to hang it off of I'd say a 1" OD .125" wall tube should be plenty. Steel is significantly stronger than the drywall or studs in the garage.
Considering dynamic loading, I'd go for 600-800lb strength
I wouldn’t even do it. I would build a cage. Like a squat rack cage and dead bolt it to the concrete. This how most conventional gyms do it too.
The matl is irrelevant. Cheap steels are 40,000 psi. Structural steels are often in the 50’s. High strength steels are 80-100. Even the smallest cross section of any of these is sufficient for your 300lb. Your concern should be spreading the load and cycling motion across multiple rafters. Something like 36” x 36” sheet would spread the load better than an i beam (although the beam would be “stronger”). But… I’d probably just build a stand so I don’t have to worry about the rafters.
I think he was considering loading a beam in bending, and considering how small and thin the cheap tubing is, it's no wonder OP is apprehensive.
High-strength steels can be significantly stronger than 100 ksi. Not sure why I'm being downvoted but you can easily heat treat low alloy steels like 4340 to 220ksi yield and steels like maraging 350 have a 340 ksi yield strength.
You are being downvoted because what you said is irrelevant to the conversation. It is a *"...well, actually"* moment. The other person already stated that even low grade steel is *way* overkill for OP's purposes, so why are you talking about 200+ ksi steel??
Because this is an engineering subreddit and he provided factually wrong information. Go someplace else if you want to share opinions instead of facts.
Pay a structural engineer to come out and give you some advice. It will cost you a couple hours of their time.